Abstract. In the process of concrete dam foundation treatment, it is often encountered that the foundation defects are beyond the expected exploration. In order to ensure the quality of the project and the progress of the construction period, the stress field of the mass concrete in the foundation pit under the condition of fast filling is studied by numerical simulation method. Based on the calculation results and engineering experience, some comprehensive measures of temperature control and crack prevention are put forward: pipe cooling + reasonable angle arrangement of antisliding anchor bar + reasonable position of the limit of crack reinforcement layout. Which can provide some reference for solving similar engineering problems.

Focus on the topography features of V-shaped deep river valley in Ada dam area, the influence of intensively, moderately and slightly weathered stratum as well as the action of river valley erosion on geostress field was considered. Then, the 3-D initial geostress unloading model was established based on the measured geostress data and geological conditions. Combining the finite element numerical method and inversion theory, multiple regression analysis was established between the measured and corresponding calculated results of geostress. Then, the optimal regression coefficient could be derived. In addition, for convenience of comparison, another method was adopted by ignoring the action of river valley erosion. Through the comparison between the computed values by two methods and the measured geostress values respectively, it is found that the computed values by the former method are more close to the measured ones. Therefore, the distribution rule of initial geostress field can be obtained accurately, which provides important reference for design and construction of Ada dam and its diversion tunnel layout.

Abstract:The gamma camera provides fast and accurate real-time imaging of the distribution of radionuclides in the human body. It can not only perform dynamic and static observations, but also can be used to observe the metabolism of local tissue organs. It is an important tool in the field of nuclear medicine. This paper introduces the principle, structure and performance index of gamma camera, and summarizes and analyzes the application and development status of gamma camera in nuclear medicine. The performance indicators of gamma cameras have been greatly improved, and have been widely used in the medical field.